A method of cladding a roof with metal sheets is the standing seam method in which the steel sheets have upstanding longitudinal edges that end with snap-on beads. The beads may then be rolled tight. The seams are so high that there could never be so much water on the roof that the water could reach the upper ends of the seams. The seams could for example be 8 cm high and, usually, full length sheets are used so that there are no transverse joints. This method is not used for cupola roofs whether or not they have constant or varied bending radius since the roofing sheets must then be bent before they are mounted. The sheets may be of metals such as steel, aluminum, zinc, or copper.
Automobile parts, such as automobile window frames and automobile door frames, are formed from hat beams or box beams. However, it is not known to form such automobile parts using a method which bends a metal sheet having upstanding sides with ends bent towards or away from the upstanding sides, by gradually thinning the upstanding sides by a pair of rollers for bending the metal sheet.